JP, I'm hardly the voice of experience, but we're halfway through our OW classes -- taking a 6-week session -- and we'll be going to the Keys next month to do our checkout dives. We had previously considered doing a trip to do the entire certification over 4 days, and I am so glad we chose to do it this way instead.
I'm finding that there's a lot of information to absorb, and it really helps me to have the week in between classes to let things "gel" a bit. I had a hard time at first with the mask-clearing skill, and went to the pool on my own time to get some practice in and feel more comfortable with it. Of course everyone is different, but if we had chosen to do it all over a few consecutive days I think it would have been overload. That's just me.
Cheers
Angie